Beginner Treadmill workout

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I am looking for some ideas for beginner treadmill workouts. I have had 3 knee surgeries so I can't do some of the high intensity ones that are out there. Since I am just beginning my weight loss adventure I am biking (recumbent) for 8 minutes then walking on the treadmill for 15 at a 0 incline and 3.3 for the speed. I want to start to push myself some more on the treadmill but so many of the treadmill specific workouts that I have seen are pretty high intense which at this point I am no where near ready for.

I am hoping that I can get some good advice/tips from you all.